Adam Clarke on 2 Corinthians 1:4

Who comforteth us - Who shows himself to be the God of tender mercy, by condescending to notice us, who have never deserved any good at his hand; and also the God of all consolation, by comforting us in all our tribulation - never leaving us a prey to anxiety, carking care, persecution, or temptation; but, by the comforts of his Spirit, bearing us up in, through, and above, all our trials and difficulties.

That we may be able to comfort them - Even spiritual comforts are not given us for our use alone; they, like all the gifts of God, are given that they may be distributed, or become the instruments of help to others. A minister's trials and comforts are permitted and sent for the benefit of the Church. What a miserable preacher must he be who has all his divinity by study and learning, and nothing by experience! If his soul have not gone through all the travail of regeneration, if his heart have not felt the love of God shed abroad in it by the Holy Ghost, he can neither instruct the ignorant nor comfort the distressed. See 2Cor 1:6.